Skid lift



May 19, A1953 R. ABERLE '2,639,150

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R. ABERLE 2,639,150

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May 19, 1953 Filled nec. 15, 1947 Boy ueife Patented May 19, 1953 SKID LIFT Roy Aberle, Portland, Maine, assignor to Southworth Machine Company, Portland, Maine,'a

company of Maine Application December 15, 1947, Serial No. 791,746

3 Claims. (Cl. 271-62) This invention relates to apparatus for automatically lifting a pile of sheet material, as paper sheets.

In cutting, punching, slotting or otherwise acting upon paper or other sheets it is customary for the operative to arrange the sheets in a pile or stack, and to withdraw random quantities of the sheets from the top of the lpile and place them in a cutter or other machine which is to operate upon them. Usually the pile of sheets is placed on a skid, and the skid moved onto a platform which is provided with jogging rails for accomplishing reasonable alinement of the sheet edges before the operative removes a quantity of sheets from the top of the pile and places them in the cutter or other machine for final squaring up and eventual cutting, punching, slotting, etc.

When the operative rst places the pile of sheets on the platform it may or may not be too high for him to most efficiently handle the sheets, working from the top of the pile downwardly, but as the height of the pile is reduced by repeatedly removing quantities of sheets from the top, the pile eventually becomes too low for eilicient handling and the operative is subjected to unnecessary fatigue. Thus, in present practice, only a relatively small section of the pile is ever positioned at the most eiiicient height for removal by the operative and by far the major portion of the pile is positioned at a height which makes for ineicient handling and worker fatigue.

The main object of my invention is to provide an automatic lift by means of which a stack or pile of sheets may be constantly maintained at a predetermined height consistent with the best eiciency of the worker in withdrawing selected quantities of sheets from the top of the pile from time to time.

Another object in to provide an automatic lift equipped with safety features which become automatically operative to lock the platform against accidental descent in the event of failure of the hoistvmechanism. A further 'object is to provide an automatic lift which is simple in construction, reliable in operation, and well suited for use as an adjunct to the conventional sheet-cutting or perforating machines now in use.

Other objects and advantages will appear as this description proceeds.

In attaining my objects, I provide a vertically movable platform on which a skid containing a stack of sheets is adapted to be placed. Jogging rails associated with the platform are adjusted r to suit the'length and width of the sheets, and a photo tube and a light sourcefocused thereon are adjusted to a predetermined height for ease of the operator in removing the sheets from the top of the stack. Initially, the light beam of the photo tube is interrupted by the stack but as the stack height is reduced by the withdrawal of sheets from the top of the stack, the light beam is established. rWheneverthis occurs an electrical sequence of relays, a pre-set'manual switch and solenoid contactors automaticallyl initiate the operation of the power unit of the machine to thereby elevate the platform and the stack of sheets a distance at which the light beam will again ybe interrupted by the stack, whereupon the power unit is automatically disconnected and the rise of the stack is stopped at a height best suited Afor efficient handling by the operative. This start and stop operation is repeated as required until the stack is exhausted.

In the accompanying drawings wherein I have shown a ,preferred embodiment of my invention:

Figure l is a perspective view of my improved lift as seen from the front of the machine, the platform being shown in partially raised position.

Fig-ure 2 is a, sectional :detail on an enlarged scale showing one of the safety devices of the machine, the safety plunger being out of operative relation to the rack with which it cooperates.

Figure 3 is a view similar to Figure 2 but showing said safety plunger in engagement with said rack.

Figure 4 is a rear elevation of my machine.

Figure 5 lis a sectional side elevation approximately on the line 5-5 of Fig. 4, and

Figure 6 is a sectional plan view on approximately the line 6'-6 of Fig. 5.

Referring to the drawings, I0 designates a substantially rectangular depression formed in a floor II. When in lowered position, skid lift platform P is received within depression IIJ with its upper surface substantially flush with the surface of the floor. Depression I0 is bounded by a pair of side angle rails I2 and a pair of end plates I3. Secured at their ends to the angle rails I2 near the rear ends of said angle rails is a pair of spaced transversely extending angle members I4 on which is mounted a drive unit base I5. The angle members I2 and end plates 'I3 lie substantially flush with the surface of the floor II.

Secured to the rear inner faces of the angle members I2 are the lower ends of a pair of spaced vertical uprightsl I I constituting the side frames of my skid lift. The side frame members i6 lie parallel to each other, and are held in spaced relation by intermediate tie bars I1 and an upper tie bar I8. Secured to the inner faces of each side frame I5, as by welding, and extending vertically thereof for a substantial distance is a safety lool; rack member I9.

Rotatably mounted in suitable bearings 2H secured to the inner faces of the side frame IG near the lower ends thereof and parallel to the upper is a drum shaft 2|. Adjacent each end of such shaft 2| and keyed thereto in the usual manner is a cable hoist drum 22. Secured to. each drum is the lower end of a hoist cable 23.

Rotatably mounted on the upper tie bar #8 adjacent each end thereof E an idler pulley 24. Each idler pulley is associated with the cable drum 22 directly below. Each cable 23 passes over the idler pulley 24 and then extends downwardly for a purpose to be hereinafter described.

Mounted on the drive unit base I is a motor or other prime mover 25 operated from a suitabley source of power, and controlled through conventional solenoid contactors (not. shown) contained in a. box 25 secured to the outer face of one of the end frames l5, such. solenoid contactors being in turnl controlled by an upper limit switch. 21, a lower limit switch 28 and a photo relay 29.

Also mounted on the drive unit base I5 and driven by the motor 25 through belts 30, is a reduction gear unit 3i. The final driving pinion 32 of the reduction gear unit 3I meshes with anddrives a spur gear 33 on. drum shaft 2l. Between its ends; the drum shaft 2.! may be journaled in a bearing 34 on top of the enclosing casing for the reduction gear unit 3l', and as a safety measure, the drumshaft spur gear 33 may be enclosed byA an enclosure 35 secured tothe lowermost tie bar I-1.

Lying parallel tothe front vertical edges of the side frames. I6 and secured thereto and to the angle member I2. atv the bottom is a pair of vertically extending lift risers 35. These risers are preferably made of channel iron, the flanges thereof forming guideways for a purpose to be later explained..

Associated with the lift risers 35 is a platform P comprised. of a plurality of channel bars 3.1 arranged parallel' to and spaced apart from each other, as shown in Fig.. 6.. Adjacent bars 31 are connected together and the platform strengthened by diagonally arranged channel bars4 38. The top faces of the channel bars 31 and 38 lie in a single plane and on such "top, faces is secured, as by welding, a plate 33 of sheet metal. Such plate 35 extends rearwardly to: a point adjacent the front vertical edge of the lift risers 36, while the rear ends of the channel bars 31 and 38 extend rearwardly of such lift risers. To the rearwardly extending ends. of the channel bars 36 are secured the lower edge of platform gussets 4D, such gussets being arranged parallel to each other and to the channel bars 31. Secured to the forward vertical edges of the gussets 4ll and to the rear edge of the plate 39, as by welding, is a rear wall or apron 4I, the front face. of which is adjacent to and lies parallel with the front vertical. edge of the lift risers 36.

The platform gussets 40 have extending therethrough, adjacent to their top and bottom ends and parallel to each other, a top shaft 42 and a bottom shaft 43 (see Fig. 4). Rotatably mounted on the outer ends. of these shafts are platform rollers 44, these rollers extending into the guideways formed in the vertical risers 36. The ends of the cables 23, which pass over the idler pulleys 24 are secured to cable thimbles 45 on the top shaft 42 adjacent to the platform rollers 44 on said shaft.

The trip lever 41 of the lower limit switch 28 lies in the path of movement of a lower limit switch trip 4S secured to the rear face of the apron 4I of the platform. The trip lever 49 0f the upper limit switch 21 lies in the path 0f movement of an upper limit switch trip 5U also secured to the rear face of the apron 4I of the platform. Therefore, when the platform appreaches` its lowermost position, the limit switch 28 cuts oil the power and the platform comes to When the platform approaches its uppermost position, the limit switch 21 cuts off the power. and the platform comes to rest in its uppermost position.

Adjacent the left front corner of the platform but independently thereof and vertically adjustable is located photo tube 5I that controls the photo relay 29, and at the right rear corner of they platform but independently thereof is 10- cated a vertically adjustable light source 52 focused upon the photo tube 5 I.

Secured to the rear face of the apron 4I, at each side thereof,v and adjacent to its upper edge are safety plungers (see- Figs. 2 and 3). Each plunger comprises a safety lock plunger tube 53, secured to the rear face of the apron 4I, as by welding, and slidably mounted in each tube 53 is a safety plunger 54, which is constantly urged to move outwardly of the tube 53 by a coil spring 55 held in position by a cover 56. Each tube 53 is provided with an elongated slot 51 to receive a pin stud 58 which screws into a threaded hole extending transversely into the plunger 54 and has an exposed portion extending outwardly beyond the tube 53'. The outer end of each plunger 54 is bevelled so as to successively engage with the teeth of the adjacent rack member I9, as the platform moves upwardly.

Pivotally mounted on the inner end of each tube 53. is a latch 59. Each latch 59 is longer than the tube 53 and has its outer end extending alongside the adjacent rack member I9. The lower face of each latch 53 is provided with a locking notch Bil in which the adjacent pin stud.- 58 is adapted to belocked (see Fig. 2). Adjustably clamped as at 6l near the upper end of each rack member I9 is a vertically disposed cam shoe or trip cam 62. Each trip Cam 62. engages the beveled end of the plunger 54 and pushes. the same further into its tube 53 than do the rack teeth on the adjacent rack member I9 when the platform reaches its upper limit of travel` This permits each latch 59 t0 fall into the position shown in Fig. 2 with the pin 58 housed in the notch 50, and thus hold the plunger 54 out of engagement with its rack member I9 as the platform descends.

When the platform reaches its lower limit of travel (see Fig. 3) the free end of each latch 59 engages with a xed trip member or stud G3 secured to each rack member I9 near its bottom end. This engagement rotates the latch 59 about its pivot, releasing the pin stud 58 so that the spring 55 will force the plunger 54 into operative relation with its rack member I9.

Thus in the upward travel of the platform, the safety plungers are continuously in engagement with the racks and when the platform reaches the limit of its upward travel, the plungers are disengaged from the rack teeth, by action of the cam shoes 62, and are locked out of action by the pins 58 entering the notches 60 of the latches 59, and so remain until released by contact of said latches with the xed studs 63 near the bottom of rack members I9.

By pre-setting the trip cams 62 to a predetermined height of skid S, it results that when all the sheets S have been removed from the skid, the empty skid itself will block the light beam across the platform and automatically disconnect the hoisting mechanism at substantially the moment that the lower ends of the cams 62 contact the plungers 54 and move the same to their locked out of action position shown in Fig. 2.

Secured to the top ends of the lift risers 36 is a guide rail support 64 having spaced tubular supports B5 along its length. Slidably mounted in the tubular supports y65 and adapted to be secured in adjusted position therein are guide rail slides 66 provided with vertically arranged slideways El in which are vertically slidable guide rails E8 (see Fig. l). These rails 68 extend downwardly toward the platform and lie in a plane parallel to and spaced apart from the apron 4l.

Secured to the left hand lift riser 35 is a bracket 69 having a slideway 10 in which is vertically slidable a guide rail 68' which is offset relative to the other rails. The rails 68 and 68 serve as guide abutments against which the stack of sheets can be jogged and aligned on the platform 39, it being noted that the rails 68 are in a common vertical plane at the rear of the platform 39 for engaging the rear face of the stack and the rail 68' is disposed to one side of the platform and in a vertical plane perpendicular to the common plane for engaging a side face of the stack.

The guide rail slides 66 are freely adjustable laterally in the tubular supports 65 and the rails Sii and 6B' will yield upwardly against gravity if a skid of sheets strikes them before all of the sheets have been removed, thereby preventing possible damage upon upward movement of the platform. Enlarged heads 'Il on the top ends of the rails 68 and 68 provide stops for limiting downward movement of the rails.

The photo tube 5| and light source 52 are set to a predetermined height for ease of handling the uppermost sheets of the skid by the operator. When the platform is loaded with a skid containing a stack of sheets and is in lowered position, the light beam from the source of light 52 to the photo tube 5| is interrupted by the stack and no movement of the platform takes place. As the sheets are gradually removed from the top of the pile on the platform, the light beam from the source of light 52 to the photo tube 5l will eventually be established, and through the electrical sequence of relays, the preset manual switch, and the solenoid contactors heretofore described will cause the power unit to start and elevate the platform and stack until the light beam is again broken, whereupon the upward movement of the stack will be stopped at approximately the operators level. When the platform is ready to be lowered, the operator needs only to throw the manual switch (not shown) for the motor 25 to cause the platform to return to ground level in position to repeat the operation after another skid of sheets has been placed thereon. It will be understood that the manual switch is adapted to control rotation of the motor in either direction.

While I have disclosed a preferred embodiment of my invention I recognize that the structure 'illustratedmay be variously modified as occasion may demand and accordingly assert for my invention a scope consistent with the appended claims.

Having thus described my invention, what I claim as new is:

l. An improved automatic lifting machine for handling a stack of sheets, comprising an upright framework, a stack supporting platform mounted for vertical movement onthe framework, means including an electric motor for moving the platform vertically on the framework, means controlled by the height vof the stack on the platform for automatically causing the motor to be energized and move the platform intermittently upwardly tothereby maintain the top level of the ystack at a predetermined height as the height of the stack is diminished by the gradual removal of the sheets from the top of the stack, safety latches carried by the platform for limiting downward movement of the platform following the intermittent upward movements thereof, means carried by `and adjustable along the upright framework for automatically moving the latches out of operative position to thereby permit return of the platform to its lowermost position, and means for automatically restoring the latches to operative position when the platform reaches its lowermost position.

2. An improved automatic lifting machine for handling a stack of sheets, comprising an upright framework, a stack supporting platform mounted for vertical movement on the framework, means including an electric motor for moving the platform vertically on the framework, a photo cell arranged at a predetermined height, means providing a beam of light focused on said photo cell in position to be interrupted by the stack on the platform for automatically causing the motor to be energized and move the platform intermittently upwardly and maintain the top level of the stack at a predetermined height as the height of the stack is diminished by the gradual removal of paper sheets from the top thereof, safety latches carried by the platform for limiting downward movement thereof following the intermittent upward movements of the platform, tripping means carried by and adjustable along the upright framework for automatically moving the latches to inoperative position when they reach the tripping means, means for holding the latches in said inoperative position during downward travel of the platform, and means for automatically releasing the last named means and restoring the latches to operative position when the platform reaches its lowermost position.

3. An improved automatic lifting machine for handling a stack of sheets, comprising an upright framework, -a stack supporting platform mounted for vertical movement on the framework, power means for moving said platform vertically on said framework, vertically arranged rack members secured to the framework independently of the platform moving means and lying parallel to each other at opposite sides of the platform, means controlled by the height of the stack on the platform for automatically applying the power means to moving the platform intermittently upwardly and thereby maintaining the top level of the stack at a predetermined height as the height of the stack is diminished by the gradual removal of sheets from the top of the stack, safety latches carried by the platform for automatically engaging the rack members independently of the platform moving means and limiting downward movement of the platform following the upward intermittent movements thereof, and tripping cams vertically adjustable to pre-set; positions along said rack members for automatically movlng said latches to inactive position when they reach the pre-set positions of the cams in the upward travel of the platform.

ROY ABERLE.

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